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<Title>Boost Graph Library: write graphviz</Title>
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<H1><A NAME="sec:write-graphviz">
<TT>write_graphviz</TT>
</H1>


<pre>
// Output graph structure without properties.
template &lt; typename VertexAndEdgeListGraph &gt;
void
write_graphviz(std::ostream&amp; out, const VertexAndEdgeListGraph&amp; g);

// Graph structure with customized property output
template &lt; typename VertexAndEdgeListGraph, typename VertexPropertyWriter &gt;
void
write_graphviz(std::ostream&amp; out, const VertexAndEdgeListGraph&amp; g,
               VertexPropertyWriter vpw);

template &lt; typename VertexAndEdgeListGraph, typename VertexPropertyWriter,
           typename EdgePropertyWriter &gt;
void
write_graphviz(std::ostream&amp; out, const VertexAndEdgeListGraph&amp; g,
               VertexPropertyWriter vpw, EdgePropertyWriter epw);

template &lt; typename VertexAndEdgeListGraph, typename VertexPropertyWriter,
           typename EdgePropertyWriter, typename GraphPropertyWriter &gt;
void
write_graphviz(std::ostream&amp; out, const VertexAndEdgeListGraph&amp; g,
               VertexPropertyWriter vpw, EdgePropertyWriter epw,
               GraphPropertyWriter gpw);

template &lt; typename VertexAndEdgeListGraph, typename VertexPropertyWriter,
           typename EdgePropertyWriter, typename GraphPropertyWriter,
           typename VertexID &gt;
void
write_graphviz(std::ostream&amp; out, const VertexAndEdgeListGraph&amp; g,
               VertexPropertyWriter vpw, EdgePropertyWriter epw,
               GraphPropertyWriter gpw, VertexID vertex_id);

// Graph structure with dynamic property output
template&lt;typename Graph&gt;
void
write_graphviz_dp(std::ostream&amp; out, const Graph&amp; g,
                  const dynamic_properties&amp; dp,
                  const std::string&amp; node_id = "node_id");

template&lt;typename Graph, typename VertexID&gt;
void
write_graphviz_dp(std::ostream&amp; out, const Graph&amp; g,
                  const dynamic_properties&amp; dp, const std::string&amp; node_id,
                  VertexID vertex_id);
</pre>

<p>
This is to write a BGL graph object into an output stream in graphviz dot format
so that users can make use of <a href="http://www.graphviz.org/">graphviz</a>
to draw a picture with nice layout.
<p>
The first version with two parameters will write the graph into a
<tt>std::ostream</tt> where each vertex is represented by its numerical vertex
ID. If users have either interior or exterior properties for each vertex
in the graph, the second version above provides a way to print those
properties into the graphviz format file. For example, if each vertex
in the graph has its label through property map object <tt>name</tt>,
users can use the second version:
<pre>
  write_graph(out, g, make_label_writer(name));
</pre>
The utility function <tt>make_label_writer</tt> returns a predefined
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> for
vertex labels.  Similarly, the third
version and fourth version require vertex
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>, edge
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>, and graph
<a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>,
respectively.

<p> The two overloads of <code>write_graphviz_dp</code> will emit
all of the properties stored in the <a
href="../../property_map/doc/dynamic_property_map.html"><code>dynamic_properties</a></code>
object, thereby retaining the properties that have been read in
through the dual function <a
href="read_graphviz.html"><code>read_graphviz</code></a>. With these
overloads, <code>node_id</code> is the name of the property map that
stores the IDs of each node for use in the output (if it is stored in
the <code>dynamic_properties</code> structure); alternatively, one may
provide an arbitrary property map for <code>vertex_id</code> giving the
vertex identifiers. In this case, the name
  of <code>node_id</code> must still be supplied to suppress its
  output as a label of the vertices.</p>

<H3>Where Defined</H3>

<P>
<a href="../../../boost/graph/graphviz.hpp"><TT>boost/graph/graphviz.hpp</TT></a>

<h3><A NAME="concept:PropertyWriter">
<tt>PropertyWriter</tt>
</h3>

PropertyWriter is used in the <tt>write_graphviz</tt> function to
print vertex, edge or graph properties. There are two types of
PropertyWriter. One is for a vertex or edge. The other is for a graph.
Thus, users could easily extend the <tt>write_graphviz</tt> function
by creating their own <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> only.
<p>
A <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>
for vertices or edges is a functor which can be called with two parameters:
<tt>std::ostream</tt> and either a vertex or an edge descriptor. It should output a
pair of brackets with a series of assigments &quot;name=value&quot; inside.
Each assignment should be separated either with space, with comma, or with semicolon.
The following functor, provided by BGL, is the example of PropertyWriter for
vertices or edges.  It is used to print the label of each vertex or edge.
<pre>
  template &lt;class Name&gt;
  class label_writer {
  public:
    label_writer(Name _name) : name(_name) {}
    template &lt;class VertexOrEdge&gt;
    void operator()(std::ostream&amp; out, const VertexOrEdge&amp; v) const {
      out &lt;&lt; "[label=\"" &lt;&lt; name[v] &lt;&lt; "\"]";
    }
  private:
    Name name;
  };
</pre>

<p>
A function to conveniently create this writer is provided:
<pre>
template &lt; class Name &gt;
label_writer&lt;Name&gt;
make_label_writer(Name n);
</pre>

<p>
A <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a>
for graphs is a functor which is called with one parameter of type
<tt>std::ostream</tt> and should print a series of graph properties. The following
code excerpt is an example of a PropertyWriter for a graph:
<pre>
  struct sample_graph_writer {
    void operator()(std::ostream&amp; out) const {
      out &lt;&lt; "graph [bgcolor=lightgrey]" &lt;&lt; std::endl;
      out &lt;&lt; "node [shape=circle color=white]" &lt;&lt; std::endl;
      out &lt;&lt; "edge [style=dashed]" &lt;&lt; std::endl;
    }
  };
}
</pre>

<p>
There exists a class <tt>default_writer</tt>, which can be used as both
vertex/edge and graph property writer, and does nothing. It is useful when
only edge properties must be written, but the function interface also requires a
vertex property writer.

<h3>Parameters</h3>
 OUT: <tt>std::ostream&amp; out</tt>
<blockquote>
  A standard <tt>std::ostream</tt> object.
</blockquote>

 IN: <tt>VertexAndEdgeListGraph&amp; g</tt>
<blockquote>
  A directed or undirected graph. The graph's type must be a model of
  <a href="./VertexAndEdgeListGraph.html">VertexAndEdgeListGraph</a>. In most cases, the
  graph must have an internal <tt>vertex_index</tt> property map.
</blockquote>

 IN: <tt>VertexPropertyWriter vpw</tt>
<blockquote>
  A functor that models <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> to print
  properties of a vertex.<br>
<b>Default</b>: <tt>default_writer()</tt>
</blockquote>

 IN: <tt>EdgePropertyWriter epw</tt>
<blockquote>
  A functor that models <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> to print
  properties of an edge.<br>
<b>Default</b>: <tt>default_writer()</tt>
</blockquote>

 IN: <tt>GraphPropertyWriter epw</tt>
<blockquote>
  A functor that models <a href="./write-graphviz.html#concept:PropertyWriter">PropertyWriter</a> to print
  properties of the graph.<br>
<b>Default</b>: <tt>default_writer()</tt>
</blockquote>

IN: <tt>dynamic_properties&amp; dp</tt>
<blockquote>
  Contains all of the vertex and edge properties that should be
  emitted by the GraphViz writer.
</blockquote>

IN: <tt>const std::string&amp; node_id</tt>
<blockquote>
  The name of the property map that provides identifiers for the
  vertices in the graph.<br>
<b>Default</b>: <tt>"node_id"</tt>
</blockquote>

IN: <tt>VertexID vertex_id</tt>
<blockquote>
  A property map that models <a href="../../property_map/doc/ReadablePropertyMap.html">Readable Property Map</a>, whose key type is the vertex descriptor of the graph, and whose value type can be written to a stream. The value should be a unique descriptor for each vertex, and will be used to name each node in the Graphviz file (it will be escaped properly for Graphviz output).<br>
<b>Default</b>: If no <code>dynamic_properties</code> object is provided, <tt>get(vertex_index, g)</tt>. Otherwise, a dynamic property map that accesses the property map in <code>dp</code> whose name is given by the <code>node_id</code> parameter.
</blockquote>
<H3>
Example
</H3>

This example demonstrates using the BGL-Graphviz interface to write
a BGL graph into a Graphviz format file.

<pre>
#include &lt;boost/graph/graphviz.hpp&gt;

enum files_e { dax_h, yow_h, boz_h, zow_h, foo_cpp,
               foo_o, bar_cpp, bar_o, libfoobar_a,
               zig_cpp, zig_o, zag_cpp, zag_o,
                 libzigzag_a, killerapp, N };
const char* name[] = { "dax.h", "yow.h", "boz.h", "zow.h", "foo.cpp",
                       "foo.o", "bar.cpp", "bar.o", "libfoobar.a",
                       "zig.cpp", "zig.o", "zag.cpp", "zag.o",
                       "libzigzag.a", "killerapp" };

int main(int,char*[])
{

  typedef pair&lt;int,int&gt; Edge;
  Edge used_by[] = {
    Edge(dax_h, foo_cpp), Edge(dax_h, bar_cpp), Edge(dax_h, yow_h),
    Edge(yow_h, bar_cpp), Edge(yow_h, zag_cpp),
    Edge(boz_h, bar_cpp), Edge(boz_h, zig_cpp), Edge(boz_h, zag_cpp),
    Edge(zow_h, foo_cpp),
    Edge(foo_cpp, foo_o),
    Edge(foo_o, libfoobar_a),
    Edge(bar_cpp, bar_o),
    Edge(bar_o, libfoobar_a),
    Edge(libfoobar_a, libzigzag_a),
    Edge(zig_cpp, zig_o),
    Edge(zig_o, libzigzag_a),
    Edge(zag_cpp, zag_o),
    Edge(zag_o, libzigzag_a),
    Edge(libzigzag_a, killerapp)
  };
  const int nedges = sizeof(used_by)/sizeof(Edge);
  int weights[nedges];
  std::fill(weights, weights + nedges, 1);

  using namespace boost;

  typedef adjacency_list< vecS, vecS, directedS,
      property< vertex_color_t, default_color_type >,
      property< edge_weight_t, int >
    > Graph;
  Graph g(used_by, used_by + nedges, weights, N);

  write_graphviz(std::cout, g, make_label_writer(name));
}
</pre>

The output will be:
<pre>
digraph G {
0 -> 4;
0 -> 6;
0 -> 1;
0 [label="dax.h"];
1 -> 6;
1 -> 11;
1 [label="yow.h"];
2 -> 6;
2 -> 9;
2 -> 11;
2 [label="boz.h"];
3 -> 4;
3 [label="zow.h"];
4 -> 5;
4 [label="foo.cpp"];
5 -> 8;
5 [label="foo.o"];
6 -> 7;
6 [label="bar.cpp"];
7 -> 8;
7 [label="bar.o"];
8 -> 13;
8 [label="libfoobar.a"];
9 -> 10;
9 [label="zig.cpp"];
10 -> 13;
10 [label="zig.o"];
11 -> 12;
11 [label="zag.cpp"];
12 -> 13;
12 [label="zag.o"];
13 -> 14;
13 [label="libzigzag.a"];
14;
14 [label="killerapp"];
6 -> 0;
}
</pre>

<p>The examples directory contains an <a
href="../example/graphviz.cpp">example using
<code>dynamic_properties</code></a>.</p>

<h3>See Also</h3>

<a href="./read_graphviz.html"><tt>read_graphviz</tt></a>

<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 2000-2001</TD><TD>
<A HREF="http://www.boost.org/people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
<A HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</A>, Indiana University (<A HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)
</TD></TR></TABLE>

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